Max Planck Institute of Colloids and Interfaces , Am Mühlenberg 1 , 14476 Potsdam , Germany.
Langmuir. 2019 Jul 2;35(26):8531-8542. doi: 10.1021/acs.langmuir.9b00191. Epub 2019 Mar 14.
Amphiphilic monolayers formed at the soft air/liquid interface are easy-to-handle and versatile model systems for material and life sciences. Helmuth Möhwald was one of the pioneers in this field. Over the last few decades, total-reflection X-ray fluorescence (TRXF) has become an important analytical tool for the investigation of monolayer interactions with ions. Here, the theoretical background of TRXF is described, and practical aspects are discussed. The experimentally determined fluorescence intensity from the adsorbed ions can be interpreted quantitatively either by a calibration procedure utilizing monolayers with known charge density or by calibration with respect to the bare aqueous surface. Both calibration approaches yield quantitatively consistent results within <10% accuracy. Some examples demonstrating the power of TRXF for the study of ion adsorption to charged and noncharged monolayers as well as for the characterization of the physicochemical properties of novel cationic lipids used for improved gene delivery are given.
在软气/液界面形成的两亲单层是易于处理且多功能的材料和生命科学模型体系。赫尔穆特·毛厄尔瓦尔德（Helmuth Möhwald）是该领域的先驱之一。在过去的几十年中，全反射 X 射线荧光（TRXF）已成为研究单层与离子相互作用的重要分析工具。本文描述了 TRXF 的理论背景，并讨论了其实用方面。通过利用具有已知电荷密度的单层的校准程序或相对于裸露的水相表面进行校准，可以对从吸附离子中实验确定的荧光强度进行定量解释。这两种校准方法都在 <10%的精度范围内得出定量一致的结果。给出了一些示例，证明了 TRXF 在研究带电荷和不带电荷的单层上离子吸附以及用于改进基因转染的新型阳离子脂质的物理化学性质表征方面的强大功能。
